build: Require yadage v0.21.0+

* Require yadage v0.21.0+ to ensure packtivity>=0.16.2 is used to
  properly handle jqlang v1.6/v1.7.
* As yadage handles the lower bounds of adage and packtivity, remove
  their stated lower bound to let the dependency resolver have yadage
  do all the work.

setup.py

@@ -3,10 +3,10 @@
 extras_require = {
  'develop': {'pytest', 'flake8>=3.9.0', 'black'},
  'local': [
+ 'yadage>=0.21.0', # yadage[viz] breaks so install following manually
+ 'adage', # compatible versions controlled through yadage
+ 'packtivity', # compatible versions controlled through yadage
  'pydotplus==2.0.2',
- 'adage>=0.10.1',
- 'packtivity>=0.14.23',
- 'yadage>=0.20.1', # yadage[viz] breaks so install following manually
  'pydot', # from yadage[viz] extra
  'pygraphviz', # from yadage[viz] extra
  ],